With large-size internal combustion engines, such as, for example, 12 cylinder diesel engines, the exhaust manifold is often formed of a series of interconnected, generally T-shaped castings, with the stem portion of each casting being connected to an exhaust gas outlet port of the engine. To permit expansion between the castings due to the high exhaust gas temperatures, it has been the practice in the past to form one arm of each T-shaped casting with an enlarged diameter which receives the smaller diameter arm of the next adjacent casting to provide a bell and spigot type slip joint. The arms of the casting are machined to extremely close tolerances to provide the sliding fit between the castings without the use of gaskets or seals. Because of the extensive machining, the conventional exhaust manifold is an expensive construction.
More recently, with higher temperature engines, the manifold castings have been formed of nickel alloys which further increases the overall cost of the manifold.